Savers and network apparatuses use various circuit boards on which semiconductor devices are mounted. Capacitor components are mounted on the surface of the circuit board for the purpose of reducing power supply noise and the like. Due to an increase in transmission rate in recent years, there is a trend toward an increase in the number of capacitor components mounted on a single circuit board.
With an increase in the number of capacitor components as mentioned above, a proportion of the capacitor components to the circuit board increases so much that a constraint is imposed on a wiring layout of the circuit board.
In addition, the capacitor components are connected to a power supply layer and a ground layer via conductor films such as plating films inside through holes. However, due to the wiring lengths of the conductor films, the inductance components of the wirings may increase so much that an increase in the transmission rate may possibly be hindered.
To address this, there have been proposed several techniques of providing capacitors inside a circuit board instead of mounting capacitor components on a surface of the circuit board.
Techniques related to the present application have been disclosed in the following documents: U.S. Pat. No. 5,010,641, U.S. Pat. No. 5,079,069, Japanese Laid-open Patent Publication No. 11-251801, and Japanese Laid-open Patent Publication No. 11-214853.